Funding is requested to purchase a new Cytomation MLS high speed cell softer to replace a 15-year-old EPICS 753 cell sorter. The Flow Cytometry Core in the Department Of Pathology at Massachusetts General Hospital (MGH) has been a continuous resource open to all basic and clinical research scientists requiring flow cytometry since 1978. The laboratory has administered and sustained itself on a combination of user fees and research grants, with departmental backing when necessary. The laboratory has a highly skilled operator and PI with documented expertise in flow cytometry, resulting in a combined 30 years of experience in flow cytometry. The need for a contemporary cell sorter is required to sustain and improve 27 ongoing NIH funded projects from combination of 10 Major and 6 Minor Principal Investigators, described in this application. The requested instrument has specifications that conservatively project an overall tenfold improvement in sorting speed and greatly improved multicolor analytic capacity, compared to the EPICS 753. The purpose of this proposal is to illustrate how the EPICS 753, which was engineered in the late 1970's, has been thoroughly utilized to its utmost capacity but is unable to attain the performance level of the current state-of- the-art instrumentation. Furthermore, Coulter-Beckman no longer services the EPICS 753. It is felt that the options requested for the new instrument are reasonable and warranted by the project summaries submitted by the contributing user groups